Agent Skills: Diagrams Skill

Diagrams Skill

Use this skill when working on Draw.io / diagrams.net files, especially architecture diagrams exported as PNGs for reviews, docs, or presentations.

Core Goal

Make the diagram easy to read in both:

• exported PNGs / documentation
• the Draw.io editor, including dark mode

Prefer clarity over density. If a diagram feels cramped, use more space instead of shrinking text.

Inputs to Review

Whenever possible, inspect all of:

1. the .drawio source
2. the exported .png
3. a screenshot from Draw.io if the user provides one

The .drawio file tells you structure. The PNG/screenshot tells you what humans can actually read.

Workflow

1. Read the .drawio XML.
2. Review the exported PNG and any editor screenshot.
3. Identify readability problems first:
   • text too small
   • text crossed by arrows
   • labels trapped in crowded boundaries
   • too much zig-zag routing
   • dark mode text disappearing
4. Adjust layout before tweaking fine details:
   • enlarge canvas
   • enlarge swimlanes / regions / panels
   • increase whitespace between columns
   • widen or heighten boxes that contain dense text
5. Simplify labels and routing.
6. Ensure shapes render above arrows.
7. Tell the user to re-export the PNG and review again.

Diagram Readability Rules

1) Spacing beats compression

• If words are hard to read, increase pageWidth, pageHeight, dx, and dy.
• Enlarge containers before reducing font size.
• Add horizontal space between major sections when cross-section arrows or labels are present.
• Add vertical space below important shapes like databases when backup / ops / notes must fit beneath them.

2) Use simpler wording in executive diagrams

• Executive diagrams should use shorter labels than implementation diagrams.
• Replace long hostnames or full repo lists with grouped labels when possible.
• Prefer concise summaries like:
  • app · get · admin · api
  • Warm DR ECS on Fargate
  • Primary writer cluster

3) Horizontal headers are easier to read

For account / region / panel containers:

• prefer horizontal swimlane headers
• avoid narrow vertical header bars when possible

4) Make text dark-mode-safe

For text-bearing shapes, set explicit text color:

• fontColor=#111111

When Draw.io dark mode causes shapes to look invisible or washed out, also consider explicit:

• opacity=100
• fillOpacity=100
• strokeWidth=2

Arrow and Routing Rules

5) Shapes must render above arrows

To avoid arrows crossing through text:

• place edge mxCells before vertex mxCells in XML order
• this keeps connectors behind boxes/clouds/notes in Draw.io rendering

6) Minimize zig-zagging

• Keep arrows as straight and direct as possible.
• Prefer one clean orthogonal bend over multiple turns.
• Use explicit waypoint points (mxPoint) when auto-routing creates noisy paths.
• For repeated vertical flows, align boxes so arrows can go straight down.

7) Don’t force important labels onto crowded edges

If edge labels become unreadable:

• remove the edge label
• add a small standalone text box in nearby whitespace instead

This works especially well in tight boundaries between accounts or regions.

8) Protect edge label readability

When an edge label must remain on the line, use:

• labelBackgroundColor=#ffffff
• fontColor=#111111

Box Sizing Rules

9) Dense boxes need more room than you think

Common offenders:

• backup boxes
• runbook / operational sequence boxes
• notes / legend boxes
• ECS boxes listing several services
• route / weight boxes with multiple lines

If text feels even slightly crowded in the PNG, enlarge the shape.

10) Notes belong in note boxes, not on spaghetti arrows

For explanatory content, prefer dashed note boxes over long edge labels. This is especially useful for:

• traffic behavior
• DB state summaries
• operational sequences
• runbook / RPO / RTO summaries

Common Review Fixes

Apply these patterns when relevant:

• Cloud text crossed by arrows → reorder edges behind shapes
• Words clipped in backup box → increase height/width
• Unreadable labels between sections → widen the gap and move text into standalone labels
• Diagram too stretched vertically but still crowded → rebalance with wider canvas and better column spacing
• Too many components for the audience → remove nonessential boxes when the user says they are not needed
• Dark mode unreadable → enforce fontColor, and if needed opacity / fillOpacity

Legend Guidance

Be explicit and consistent. Preferred wording:

• Solid lines = primary live production path
• Dashed lines = standby, replication, or failover path

If some dashed lines are operational/admin paths, make sure the legend still matches the real meaning or call out exceptions.

ID Safety Rules

When rebuilding or duplicating sections in .drawio XML:

• never reuse mxCell IDs for different objects
• use distinct ID ranges for alternate states or duplicated panels
• if a section goes missing after edits, suspect ID collisions first

Practical Editing Guidance

• Use edit for small targeted changes.
• Use write for full diagram rewrites or XML rebuilds.
• After major layout changes, re-read the .drawio to verify IDs, geometry, and styles are valid.
• If a user is iterating from screenshots, expect multiple review/export rounds.

Quality Checklist

Before calling the diagram ready, verify:

• all important words are readable in the PNG
• nothing important is hidden behind arrows
• edge routing is mostly straight and intentional
• section spacing feels generous, not cramped
• labels are concise enough for the audience
• dark mode still shows text clearly in Draw.io
• legend wording matches the actual line semantics

For more detailed guidance, see the Draw.io reference.